package chapter2;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.Key;

/**
 * Basic example using the KeyGenerator class and
 * showing how to create a SecretKeySpec from an encoded key.
 */
public class KeyGeneratorExample {
    public static void main(
            String[] args)
            throws Exception {
        byte[] input = new byte[]{
                0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
                0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
                0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};
        byte[] ivBytes = new byte[]{
                0x00, 0x00, 0x00, 0x01, 0x04, 0x05, 0x06, 0x07,
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01};

        Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding", "BC");
        KeyGenerator generator = KeyGenerator.getInstance("AES", "BC");

        generator.init(192);

        Key encryptionKey = generator.generateKey();

        System.out.println("key   : " + Utils.toHex(encryptionKey.getEncoded()));

        System.out.println("input : " + Utils.toHex(input));

        // encryption pass

        cipher.init(Cipher.ENCRYPT_MODE, encryptionKey, new IvParameterSpec(ivBytes));

        byte[] cipherText = new byte[cipher.getOutputSize(input.length)];

        int ctLength = cipher.update(input, 0, input.length, cipherText, 0);

        ctLength += cipher.doFinal(cipherText, ctLength);

        // decryption pass

        Key decryptionKey = new SecretKeySpec(encryptionKey.getEncoded(), encryptionKey.getAlgorithm());

        cipher.init(Cipher.DECRYPT_MODE, decryptionKey, new IvParameterSpec(ivBytes));

        byte[] plainText = new byte[cipher.getOutputSize(ctLength)];

        int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);

        ptLength += cipher.doFinal(plainText, ptLength);

        System.out.println("plain : " + Utils.toHex(plainText, ptLength) + " bytes: " + ptLength);
    }
}
